diff --git a/lib/behat/classes/behat_session_trait.php b/lib/behat/classes/behat_session_trait.php
index 02e914edd8f..62b6fd6d968 100644
--- a/lib/behat/classes/behat_session_trait.php
+++ b/lib/behat/classes/behat_session_trait.php
@@ -761,9 +761,14 @@ trait behat_session_trait {
      *
      * @param string $windowsize size of window.
      * @param bool $viewport If true, changes viewport rather than window size
+     * @param bool $scalesize Whether to scale the size by the WINDOWSCALE environment variable
      * @throws ExpectationException
      */
-    protected function resize_window($windowsize, $viewport = false) {
+    protected function resize_window(
+        string $windowsize,
+        bool $viewport = false,
+        bool $scalesize = true,
+    ): void {
         global $CFG;
 
         // Non JS don't support resize window.
@@ -807,6 +812,16 @@ trait behat_session_trait {
             $height *= $CFG->behat_window_size_modifier;
         }
 
+        if ($scalesize) {
+            // Scale the window size by the WINDOWSCALE environment variable.
+            // This is intended to be used for Behat reruns to negate the impact of browser window size issues.
+            // This allows a per-run, runtime configuration of the scaling, unlike behat_window_size_modifier which
+            // typically applies to all runs.
+            $scalefactor = getenv('WINDOWSCALE') ? floatval(getenv('WINDOWSCALE')) : 1;
+            $width *= $scalefactor;
+            $height *= $scalefactor;
+        }
+
         if ($viewport) {
             // When setting viewport size, we set it so that the document width will be exactly
             // as specified, assuming that there is a vertical scrollbar. (In cases where there is
diff --git a/lib/tests/behat/behat_general.php b/lib/tests/behat/behat_general.php
index d03c42b0b40..491a5decca9 100644
--- a/lib/tests/behat/behat_general.php
+++ b/lib/tests/behat/behat_general.php
@@ -1331,12 +1331,22 @@ EOF;
      * browser window has same viewport size even when you run Behat on multiple operating systems.
      *
      * @throws ExpectationException
-     * @Then /^I change (window|viewport) size to "(mobile|tablet|small|medium|large|\d+x\d+)"$/
-     * @Then /^I change the (window|viewport) size to "(mobile|tablet|small|medium|large|\d+x\d+)"$/
+     * @Then /^I change (window|viewport) size to "(mobile|tablet|small|medium|large|\d+x\d+)"( without runtime scaling)?$/
+     * @Then /^I change the (window|viewport) size to "(mobile|tablet|small|medium|large|\d+x\d+)"( without runtime scaling)?$/
+     * @param string $windowviewport Whether this is a window or viewport size hcange
      * @param string $windowsize size of the window (mobile|tablet|small|medium|large|wxh).
+     * @param null|string $scale whether to lock runtime scaling (string) or to allow it (null)
      */
-    public function i_change_window_size_to($windowviewport, $windowsize) {
-        $this->resize_window($windowsize, $windowviewport === 'viewport');
+    public function i_change_window_size_to(
+        $windowviewport,
+        $windowsize,
+        ?string $scale = null,
+    ): void {
+        $this->resize_window(
+            $windowsize,
+            $windowviewport === 'viewport',
+            $scale === null,
+        );
     }
 
     /**